The present disclosure relates to a retaining member for preventing undesired detachment of a roller, a shaft, and a gear provided around the roller or the shaft in a drive unit, and image forming apparatuses, such as a copier, a printer, a facsimile machine, and a multifunction peripheral having functions of these, which are provided with such a retaining member.
In conventional image forming apparatuses, such as copiers and printers, a drive transmission mechanism composed of a gear, a shaft, and the like for transmitting a rotational driving force of a drive unit is used to transmit the rotational driving force to rotary bodies such as a photosensitive drum, a developing roller, and the like, which are driven members. In such a drive transmission mechanism, as a method to prevent undesired detachment of a roller, a shaft, and a gear provided around them, there has been used a method in which a retaining ring such as an E-ring is provided around the shaft.
As for image forming apparatuses, there has been an increasing demand for compactness, and this puts a strict restriction on the design of the drive transmission mechanism in terms of space. In the method where the conventional retaining member such as an E-ring is used, it is necessary to fit the retaining member from a radial direction of a roller or a shaft, and this disadvantageously requires a space in the radial direction for the fitting and makes the attaching/detaching operations disadvantageously complicated. Furthermore, end parts of the roller and the shaft are exposed, and this disadvantageously allows leakage of bearing grease at the end parts.
There is also known a gear retaining structure in which a gear is fitted to a fixed shaft standing on a plate-shaped member made of resin, and an elastically deformable claw-shaped projection projecting from the plate-shaped member is provided, such that a claw part of the claw-shaped projection engages with a rim of the gear fitted to the fixed shaft.
There is also known a retaining member which has inner and outer circumferential portions, a connection portion, a plurality of engagement projections, and a slit, and which is integrally formed of an elastically deformable material. To fit the retaining member to a shaft, it is pushed from the axial direction of the shaft to open the slit and elastically deform the inner circumferential portion, and the engagement projections are engaged with an engagement groove. To remove the retaining member from the shaft, it is pulled in the axial direction of the shaft while also being pulled in the radial direction of the shaft such that the inner circumferential portion is elastically deformed.